 This massive avalanche of rock and ice took out the top of Rainier, bringing its height down to around .About 530 to 550 years ago, the Electron Mudflow occurred, although this was not as large-scale as the Osceola Mudflow.While the Cascade volcanic arc (a geological term) includes volcanoes such as the Mount Meager massif and Mount Garibaldi, which lie north of the Fraser River, the Cascade Range (a geographic term) is considered to have its northern boundary at the Fraser.